1. Field of the Invention
The present invention relates to a switch.
2. Description of the Related Art
As a switch for converting a path of a high frequency signal used in wireless communications, for example, a high electron mobility transistor (HEMT) of a GaAs based compound semiconductor is used. However, the price of a compound semiconductor wafer may be relatively high, and a large aperture of wafer thereof is currently not provided, and thus, it is disadvantageous in terms of price.
In addition, recently, in order to reduce the price of switches, for example, a complementary metal oxide semiconductor (CMOS) switch has been developed. A general CMOS (bulk CMOS) may cause power leakage due to a low-resistance substrate, and the switching characteristics thereof may be deteriorated. Accordingly, for example, when a CMOS switch is used, special processes using, for example, a silicon on sapphire (SOS) process or a silicon on insulator (SOI) process are used to improve switching characteristics. However, when special processes such as a SOS process, a SOI process or the like are used, manufacturing costs of the switch are increased.
Under these circumstances, technologies related to switches for converting a path of a high frequency signal have been developed. For example, Patent Document 1 discloses a technique related to switches using a heterojunction bipolar transistor (HBT).
For example, when a switch is formed using a bipolar transistor such as a heterojunction bipolar transistor (HBT) in which a general process such as a SiGe BiCMOS process, a combination of a SiGe HBT process and a bulk complementary metal oxide semiconductor (CMOS) process, is used, the costs of the switch may be reduced, as compared to when a switch is formed of a field effect transistor (FET) such as a high electron mobility transistor (HEMT). Here, as a FET has a symmetrical structure (that is, a structure in which a drain and a source are not fixed), the FET has the same characteristics when operating both in forward and reverse directions with respect to an amplitude of a high frequency signal. Meanwhile, in a bipolar transistor, operating characteristics in forward and reverse directions are not the same. Consequently, in a switch in which a bipolar transistor is used, distortion with respect to the amplitude of a high frequency signal may be generated.
For example, according to Patent Document 1,the characteristics of an HBT are improved, and thus there is a possibility of reducing distortion with respect to the amplitude of a high frequency signal. However, when using the technique disclosed in the Patent Document 1,a special process has to be used, and thus cost reduction cannot be expected.
[Related Art Document]
    (Patent Document 1) Japanese Patent Laid-Open Publication No. 2006-279316